Method and a device to measure electromagnetic radiation from or reception of from outside coming electromagnetic radiation in a circuit card

ABSTRACT

In order to measure radiation emitted from or the influence of radiation on an individual circuit board, which in use normally is arranged in a rack in parallel to other circuit boards, all circuit boards being connected to a common backplane, the backplane is modified in such a way that the connection of a considered board will be located on the opposite side of said backplane compared to the connections of the others boards. The whole equipment is located in a shielded housing except the considered circuit board. Thus the radiation from the other circuit boards will be shielded or attenuated and only the radiation from the considered circuit board will contribute to the radiation field around the device. In the same way only this considered circuit board will be sensitive to electromagnetic radiation arriving from the outside. The power supply of the device is preferably provided by power equipment located inside the shielded housing, such as a battery as well as a direct voltage power adaption unit.

BACKGROUND

The present invention relates to measuring electromagnetic emission fromcomponent or circuit boards mounted in racks, i.e. in the usual way inparallel to each other with a common connection plane, on one side ofwhich the connections to the boards are located. The invention alsorelates to measuring interference sensitivity to electromagneticradiation coming from the outside in such an individual component orcircuit board, i.e. the influence of the radiation on the signaltransmission between the electronic circuits on the board and therefromto the connections of the board in the connection plane.

Authorities in different countries make ever harder demands on theamount of electromagnetic radiation which is allowed to be emitted byelectronic equipment. Emission of electromagnetic radiation thus must berestricted as much as possible. For electronic equipment, in whichseveral component or circuit boards are mounted in parallel in a commonconnection plane, there is for natural reasons particular difficultiesin measuring the emitted radiation from each individual board.

From the document AT & T Technologies, Technical Digest No. 73, January1984, "Circuit Pack Adaptor for High-Speed Circuit Packs", it is, in thetesting of electronic equipment previously known to mount an individualcircuit board on the rear side of the backplane or connection planeconventionally used in a computer. This mounting of the individual boardmakes the conductors on the board accessible for connection to electrictesting equipment. The device mentioned in this document can however notbe used for the measurement of the electromagnetic radiation which isemitted from the circuit board connected at the rear side, sinceradiation emitted from this card is mixed with the radiation emittedfrom the other boards. Nor is this device suited to be used for testingthe interference sensitivity of an individual board, since a possiblefault appearing in the electronic device, as a whole, of which anindividual board is a part, not securely can be traced to have appearedin this board.

SUMMARY

For measuring the emission from and radiation effects on an individualboard a method and a device are provided, the more detailedcharacteristics of which appear below.

Thus a backplane or connection plane is used being principally of thekind disclosed in the document cited above. In addition however, allother component or circuit boards than that to be tested, are enclosedby suitable electrical and/or magnetic shieldings. Hereby themeasurement is not disturbed by radiation emitted from the othercomponent or circuit boards. Nor will faults appear in the shieldedboards except possibly in the board which is tested and which protrudesfrom the rear side of the connection plane. The board which is testedthen suitably protrudes through a slot in the shielding, which in thesimplest embodiment is an electrically conducting, grounded housing.

On one side of this housing, which is located adjacent to the boardwhich is tested, ferrite material may be arranged to provide also amagnetic shielding. Also the slit area itself, through which the boardprotrudes from the housing, can be covered by a ferrite plate. It isthen provided with appropriate openings for connection pins orconnection leads to the component or circuit board which is to betested.

For some boards also advantageously a lower and/or an upper ground planemay be arranged, which are located in an angle perpendicular to thesurface of the board. This or these extra ground planes are furtheradvantageously also coated by ferrite material on the side facing thetested board.

Further the device should in the testing operation be operated by abattery power source, possibly supplemented by an appropriate voltageconverting assembly for production of various suitable supply voltages.

BRIEF DESCRIPTION OF THE DRAWING

The invention will now be described with reference to the accompanyingdrawings, in which

FIG. 1 shows a perspective view of a device for the measurement ofemission from and the influence of incoming radiation on an individualboard, where the lid is removed for the sake of visibility, and

FIG. 2 shows a shielding plate for use in interference suppression ofthe connection slit for a board.

DESCRIPTION DESCRIPTION

An electronic equipment comprises in the common way several component orcircuit boards. The boards are mounted in the cabinet or in a rack andare all electrically connected to the same side of a common backplane orconnection plane. The backplane is in the usual way constituted by acircuit board with suitable connection plugs or sockets for theindividual component or circuit boards.

In FIG. 1 is shown, in a perspective view, how the electronic equipmentis modified for testing an individual board. When a person thus wants tomeasure the electromagnetic emission from an individual component orcircuit board 7, the person produced a backplane 3, which has the sameconfiguration as the backplane used in the ordinary operation of theoriginal electronic equipment but with the exception that theconnection, i.e. the socket 9, for the circuit board 7, which is to betested, is located on the opposite side of the backplane 3, compared tothe other connections 5 for the other component or circuit boards 1. Itmeans, that the connections of the individual conductors on the board tothe socket 9 will be located in such a way that they correspond to amirrored image with reference to the centre of the socket of theoriginal connections for a corresponding circuit board which is notdisplaced.

The backplane 3 configured in this way is then equivalent in theoperation to the original backplane and the electronic equipmentconstructed with a modified backplane is naturally also equivalent tothe original electronic equipment, provided that the other components inelectronic equipment are unchanged.

The backplane 3 is placed with its connected component and circuitboards 1 and 7 in a shielded housing 11 together with other suitablecomponents in the electronic equipment. The housing 11 consists, as isshown in the Figure, of a rectangular housing with a bottom, sides and alid (the lid is not shown in the figure). The lid is provided with anopening 13, through which the circuit board 7, which is to be tested,protrudes. Further, the power supply for the electronic equipment isarranged in the shielded housing 11, such as indicated with the battery15 and an assembly 17 for obtaining appropriate direct voltages based onthe direct voltage of the battery 15.

Alternatively the equipment may be supplied by means of an exteriorconnection 19, in the figure drawn with dotted lines, in that case theassembly 17 being a conventional direct voltage power unit. Theconnection line 19, when it is connected to an exterior voltage source,must be very well shielded.

In a measurement the device is started and then also the lid not shownin FIG. 1 is mounted on the shielded housing 11. For measurement ofemission further the electronic equipment as a whole is installed on aplace which is free from extra electromagnetic fields, such in a freefield measuring place or in an electromagnetically attenuated roomcoated by attenuating plates or with attenuating cones. A receiverantenna, schematically indicated at 20, is placed on different positionsin the neighbourhood of the electronic equipment and is connected to ananalysis equipment (not shown), whereby an emission field can bedetermined or for instance only the maximum direction of the emittedelectromagnetic radiation.

The shielded housing 11 is further grounded by means of a ground cable21 and in order to further improve the shielding of radiation,originating from the interior of the shielded housing 11, one side ofthe shielded housing may be coated with ferrite plates 23. It is madepreferably only on the side of the housing 11, which has the opening 13for the board 7 which is to be tested. Also the shielding of the opening13 in this side can be improved by placing a ferrite plate 25 in theopening. The ferrite plate is, as is shown in FIG. 2, provided with anumber of holes 27, through which the connections in the shape of forinstance pins from the board 7 or alternatively from the socket 9extend.

Boards having frontal connections and a special grounding can forshielding purposes require a supplement in the shape of an extra groundplane 27 carrying a board guide 29, e.g. as normally made of plasticsmaterial. Advantageously the ground plane 27 is coated by ferrite plates31. The ground plane 27 protrudes from the shielded housing 11 and isarranged in an angle perpendicular to the board 7 which is to be tested.Such ground planes 27 can be arranged both at the lower and the upperedge of the board if required. Suitable board guides similar to the oneindicated at 29 are in addition also advantageously used, when extraground planes 27 are not used.

In certain cases the ferrite plates, both at the rear side and on theextra ground planes, can, for enhancing the attenuation for very highfrequencies, by supplemented by cones of attenuating material (notshown).

Above the invention has been described for the case of measuring theemission from an individual component board. When the resistance of theelectronic equipment to electric interferences or disturbances insteadis to be tested, the equipment is like above started and suitableelectromagnetic external waves are generated by means of someappropriated sender antenna, like the one indicated at 20. The emissionfield of the antenna should then be known. In operation of electronicequipment and when varying the radiation field, the power and frequencyand direction thereof, it is detected in the electronic equipmentwhether any disturbances of the operation appear. Therefore suitably anexterior analysis equipment 33 is arranged, having another, very wellshielded connection 35 to the electronic circuits in the shieldedhousing 11.

What is claimed is:
 1. A method of facilitating measurement ofelectromagnetic emission from or reception of electromagnetic radiationby an individual circuit board in an electronic device to be tested,wherein the individual circuit board is arranged in parallel to othercircuit boards, and the boards all have electric connections arranged atthe same side of a backplane common to the boards, comprising the stepsof:producing a connection to a backplane which is electricallyequivalent to a backplane normally used in the electronic device to betested, with the exception that the produced connection which is to beused for the individual circuit board is located on a side of theproduced backplane which is opposite to a side where all otherconnections to the other circuit boards are located; placing all circuitboards in their connections in the produced backplane, whereby anelectronic device is obtained, which in the functioning thereof isequivalent to the electronic device to be tested; arranging an electricshielding around the other circuit boards in the obtained electronicdevice except the individual circuit board to be tested; and startingthe obtained electronic device modified in this way and measuringelectromagnetic emission from or reception of electromagnetic radiationcoming from outside the electronic device.
 2. A method according toclaim 1, wherein at least partly a magnetic shielding is arranged as asupplement to the electric shielding.
 3. A method according to claim 1,wherein the shielding comprises an electrically conducting housingconnected to ground.
 4. A method according to claim 3, wherein theconductive housing has a side which is located adjacent to the producedbackplane, and that this side is covered by a ferrite material.
 5. Amethod according to claim 1, wherein the electric shielding is providedwith a slit shaped opening, through which the individual component orcircuit board extends.
 6. A method according to claim 5, wherein theslit shaped opening is provided with a coating of ferrite material, inwhich holes are made, for passing electric connection leads to theindividual component or circuit board.
 7. A method according to claim 1,wherein an electrically shielding plane is arranged at a lower edgeand/or an upper edge of the individual component or circuit board andperpendicularly to the board.
 8. A method according to claim 7, whereinthe electrically conducting shielding plane is connected to ground.
 9. Amethod according to claim 7, wherein the electrically conductingshielding plane is covered by a ferrite material.
 10. A method accordingto claim 3, wherein the electronic device is started by connecting it toa battery power source located in the shielded housing.
 11. A device forfacilitating measurement of electromagnetic emission from or receptionof electromagnetic radiation by an individual component board in anelectronic device to be tested, wherein the individual component boardis arranged in parallel to other component boards, and the boards allhave electric connections arranged at the same side of a connectionplane common to the boards, and when measuring the electromagneticemission, an electronic device is obtained, which in the functioningthereof is equivalent to the electronic device to be tested, is intendedto be used together with a means for measuring electromagneticradiation, the obtained device comprising a connection plane, which issimilar to the connection plane used in the electronic device to betested, with the exception that a produced connection, belonging to theindividual component board, is located on a side of the producedconnection plane which is opposite to a side where all other connectionsto the other component boards are located;wherein all component boardsare placed in their connections in the produced connection plane of theobtained electronic device and the obtained electronic device inaddition comprises all the components included in the electronic deviceto be tested, and an electric shielding arranged around the othercomponent boards except the individual component board, wherein theobtained device, when used for measuring the reception ofelectromagnetic radiation coming from outside the measuring device,comprises means for measuring this reception.
 12. A device according toclaim 11, wherein at least partly the electric shielding is supplementedby a magnetic shielding.
 13. A device according to claim 11, wherein theshielding comprises an electrically conducting housing connected toground.
 14. A device according to claim 11, wherein the conductivehousing comprises a side located adjacent to the backplane of themeasuring device and that this side is covered by a magnetic shieldingsuch as made of ferrite material.
 15. A device according to claim 11,wherein the electric shielding is provided with a slit shaped opening,through which the individual component or circuit board extends.
 16. Adevice according to claim 15, wherein the slit shaped opening isprovided with a coating of a magnetically shielding material such asferrite material, in which holes are made, for passing electricconnection leads to the individual component or circuit board.
 17. Adevice according to claim 11, wherein an electrically conductiveshielding plane is arranged at a lower edge and/or an upper edge of theindividual component or circuit board.
 18. A device according to claim17, wherein the electrically conductive shielding plane is connected toground.
 19. A device according to claim 17, wherein the electricallyconductive shielding plane is covered by a magnetically shieldingmaterial such as ferrite material.
 20. A device according to claim 11,wherein the measuring device comprises a connection to a battery powersource and that the connection and the power source are located insidethe electric shielding.